Ketones, a-phenylthio

The reaction of crotonaldehyde and methyl vinyl ketone with thiophenol in the presence of anhydrous hydrogen chloride effects conjugate addition of thiophenol as well as acetal formation. The resulting j3-phenylthio thioacetals are converted to 1-phenylthio-and 2-phenylthio-1,3-butadiene, respectively, upon reaction with 2 equivalents of copper(I) trifluoromethanesulfonate (Table I). The copper(I)-induced heterolysis of carbon-sulfur bonds has also been used to effect pinacol-type rearrangements of bis(phenyl-thio)methyl carbinols. Thus the addition of bis(phenyl-thio)methyllithium to ketones and aldehydes followed by copper(I)-induced rearrangement results in a one-carbon ring expansion or chain-insertion transformation which gives a-phenylthio ketones. Monothioketals of 1,4-diketones are cyclized to 2,5-disubstituted furans by the action of copper(I) trifluoromethanesulfonate. ... 

Ring expansion.1 The adducts (2) of cycloalkanones with 1 on reaction with methyllithium or wc-butyllithium at 0° rearrange to ring-expanded a-phenylthio ketones. 

Intermediate 3 can either be isolated or used in situ for further elaboration. Fluoride-5 and Lewis-acid catalyzed aldol reactions cleanly give aldol adducts,5 and the reaction with phenylsulfenyl chloride gives a-phenylthio ketones in high yield.5... 

Silveira, C. C. Bemardi, C. R. Braga, A. L. Kaufman, T. S. Elaboration of 1-benzoyltetra-hydroisoquinoline derivatives employing a Pictet-Spengler cyclization with a-chloro a-phenylthio ketones. Synthesis of O-methyl-velucryptine. Tetrahedron Lett. 2001, 42, 8947-8950. 

Reduction of a-methylthio ketones, a-Methylthio and a-phenylthio ketones (1) are reduced with high selectivity to sy/i-alcohols (2) by this complex hydride, except when... 

A similar reaction with sodium benzenethiolate results in a-phenylthio ketones. Example ... 

The oxidation of sulfides to sulfoxides is a facile transformation for which many reagents have been employed in the literature. These include hydrogen peroxide, ozone, nitric acid, chromic acid or tert-butylhypochlorite. Here, meto-chloroperbenzoic acid is used to oxidize a-phenylthio ketone 14, and successive elimination of the resulting a-phenylsulfinyl ketone 15 by heating at reflux in benzene provides the or,ji3-unsaturated ketone 16. Because of their thermal instability sulfoxides easily undergo elimination. The mechanism is explained by Cram as stereospecific cw-elimination. ... 

The reactions with esters of stabilized anions (32) and (38) give a-phenylthio ketones in yields of 75-82% (equation 37).2 Acylations with succinic anhydride and butyrolactone to give y-keto acids and y-hydiDxy ketones respectively, also proceed in good yields. ... 

Methoxy-a-(phenylthio) ketones, e.g., 3-methoxy-l-phenyl-2-phenylthiopropanone and 5-methoxy-l-phenyl-4-phenylthio-l-penten-3-onc (Table 6), can also be reduced with syn selectivity by zinc borohydride. calcium borohydride and lithium triethylborohydride82. For zinc and calcium borohydride, at least, it is reasonable to suppose that the transition state 4 (where R3 = MOM) is reinforced by /1-chclation. These reagents are actually more successful than L-Selectride in the reduction of 3-methoxy-1-phenyl-2-phenylthiopropanone, where the L-Se-lectridc result is anomalously poor. A /5-hydroxy substrate, 3-hydroxy-2-mcthylthio-l-phenyI-propanone, could be reduced to 2-methylthio-l-phenyl-l,2-propanediol with good syn selectivity using zinc borohydride (yield 65% d.r. 93 7)81. 

Chiral a-phenylthio ketones may be prepared in good yields and high by the reaction of tin (II) enolates with thiosulphonates in the presence of chiral diamines (Scheme 32). 

Desulfurization. Japanese chemists have found that a-phenylthio ketones are desulfurized by zinc and chlorotrimethylsilane in ether as shown in equation (I). 

Phenylthio-2-cyclopentenone, 33 a-Phenylthio ketones, 532-533 l-Phenylthio-2-methoxy-1,3-butadiene,... 

In a-phenylthio-ketones the phenylthio-group enhances both the kinetic and thermodynamic acidity of the proton on the sulphur-bearing carbon. The position of equilibrium in equation (1) was determined by trapping with trimethylsilyl chloride and subsequent analysis under conditions in which the rate of silylation exceeded... 

Warren has discussed the chemistry of adducts from bis(phenylthio) carbanions and carbonyl compounds. The intriguing differences observed between the reactions of trifluoroacetic acid and tosic acid with the aldehyde adducts have led to syntheses of ketones and a-phenylthio-ketones (Scheme 9). 

The tosic acid-catalysed rearrangement of or-hydroxythioacetals (65) to a-phenylthio-ketones has been discussed in an earlier section (see Scheme 9). a-Thioethyl-ketonitriles (66) have now been prepared from aldehydes in good yields, but the full synthetic potential of these compounds has yet to be explored. ... 

Addition of PhMe2SiLi to a-phenylthio ketones directly affords sUyl enol ethers with very high (Z)-stereoselectivity (eq... 

The reaction of (2) with esters provides a-phenylthio-a-tri-methylsilyl ketones, which can be easily converted to a-phenylthio ketones (eq 6). /3-Hydroxy sulfides are obtained from the reaction of (1) with carbonyl compounds in the presence of a catalytic amount of fiuoride ion (eq 7). ... 

A catalytic, enantioselective, Lewis base (313)-catalysed a-sulfenylation of silyl enol ethers (311) has been developed by Denmark et al. (Scheme 84). Among a wide variety of chiral Lewis bases investigated in this reaction, selenophosphoramides (313) afforded a-phenylthio ketones (312) in generally high yield and with good enantioselectivity. The selectivity of the reaction did not depend on the size of the silyl group... 

Sulphenylation with a sulphenamide occurs in the formation of sulphides from an JV-alkylthio-phthalimide or -succinimide with a Grignard reagent or an alkyl-Iithium compound, respectively, and in the formation of a-phenylthio-ketones from enamines and (PhSlsN. ... 

Trost has published additional applications of a-lithiocyclopropyl phenyl sulphide, including an approach to spiro-sesquiterpenes, involving geminal alkylation, which utilizes a process that is formally the reversal of dithian-carbonyl addition(also see related studies by Marshall Synthetic applications of the highly nucleophilic methoxy-phenylthio-methyl-lithium PhSCH(Li)OMe and of the acyl anion equivalent methylthioacetic acid dianion RSCHCLOCOgLi (R = Me or Ph ) have also been described, as have synthetic procedures based on anions of a-alkylthio- or a-phenylthio-ketones and methylthiomethyl dithiocarbamates. ... 

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